1. Field of the Invention
The present invention relates to a vehicular infrared irradiation lamp, and, more specifically, relates to a structure of a light-emitting element and a reflector in an irradiation lamp.
2. Related Art
A vehicular headlamp apparatus can generally change between a high beam and a low beam. The low beam irradiates the vicinity at a predetermined brightness, and is mainly used for city driving where regulations for light distribution are established so that oncoming and preceding vehicles are not dazzled. Meanwhile, the high beam irradiates a broad range ahead and in the distance at a comparatively high brightness, and is mainly used for high-speed driving on roads with few oncoming or preceding vehicles.
Compared to the low beam, the high beam excels in terms of the driver's visibility. However, the high beam also dazzles the driver of a vehicle (referred to as a preceding vehicle below) traveling in front of the host vehicle. A smart beam system avoids this by including a high/low switch lamp in which a solenoid drives a movable shade to switch between the high beam and the low beam. The smart beam system automatically switches between the high beam and the low beam depending on the conditions around the vehicle. In a vehicle having this smart beam system, an infrared irradiation lamp for determining conditions ahead of the vehicle may be provided in the headlamp. Based on the reflected infrared light projected from the infrared irradiation lamp, the high beam is projected when there is no preceding vehicle and the high beam is automatically switched to the low beam when there is a preceding vehicle present. Thus, the high beam can be selected as often as possible to secure a good field of vision without dazzling preceding vehicles.
When a red light-emitting diode is used as a light source of the infrared irradiation lamp, red visible light may be reflected by a reflector and observed ahead of the lamp. However, installation at the front of the vehicle in this state is not permitted and poses a problem from a legal standpoint. Hence, a vehicular headlamp is described in Patent Document 1 that arranges a semiconductor light-emitting element for visible light and a semiconductor light-emitting element for infrared light in parallel. Both the visible light and infrared light are reflected by a reflector to obscure the redness of the infrared light-emitting element.    [Patent Document 1] Japanese Patent Application Laid-Open (Kokai) No. 2004-241138